Artificial silk



Patented Jan. 10, 1939 UNITED STATES PATENT OFFICE ARTIFICIAL SILK Richard Miiller, Berlin-Schoneberg, and Alfred Liibke, Mannheim-Waldhof, Germany, assignors to C. F. .Boehringer & Soehne G. m. b. IL, Mannheim-Waldhof, Germany No Drawing. Application February 7, 1934, Se-

rial No. 710,113. In Germany February 15,

1 Claim. (01. 18-54) The present invention relates to the production Example 2 of artificial silk and similar artificial products In a Similar manner and with the same including ribbons films r especially m zle a. similar solution ofv cellulose triacetate was cellulose esters of carboxyhc acids, and one of its precipitated in toluene objects is the production of products of this kind,

which are mechanically stronger than similar Titer f Swen th I products hitherto produced. i gg g e ig sin r Elvnglafion sin lct regd It has been found that if solutions of cellulose tgti ng bgth 11in; goli t ion per cent in gg esters of carboxylic acids are. spun in accordance with the wet spinning process, the mechanical strength of the threads, ribbons, films or the jfgt 1:16 M8 20 5 U0 like is increased if the coagulation of the esters +17 1:15 1. 2015 109 takes place in precipitating liquors kept at a low :23 g; 5- temperature. Already at a temperature ap- +40 1216 2108 15 1Is1 15 proaching 0 C., for instance at +2 a stronger :gg {3% 3 5 5'83 product is obtained and if the temperature is lowered further, for instance to 10 and Example 3 40 and further down a further increase of strength is bt A solution of a cellulose triacetate hydrolized In order to demonstrate the i flu f low to the extent of containing 59.7% acetic acid and temperatures of the o d mentioned above on dlssolved in methylene chloride-alcohol (95:5) the strength of the artificial thread, ribbon or was Spun and Preclpltated 111 etherfilm, we will now proceed to give the results of I some of many comparative tests made with dif- Temperature oencent e g g g Elongation ferent esters and precipitating liquors at differ- P V1011 thread: in grams per 0;, tating bath rung solutlon percent ent temperatures. demers demer Example 1 Dames A fibriform cellulose triacetate washed and 3;, {g5 50 dried in the usual manner was dissolved in a fig mixture formed of 95 parts by volume methylene '15 chloride and 5 parts alcohol, the concentration -10 1111 2.45 13 1.92 of the solution used in the difierent tests being shown in the following schedule in cubic centi- Example 4 .15 of the solvent j fi of the i k The A cellulose diacetate dissolved in the same solu long 9 m e manner We f vent mixture was precipitated in ether. in the wet spinning process with a draft velocity of 10 to 20 metres per minute through a nozzle Titer of Strength of formed with 36 holes, each 0.08 millimetre 1n single ff single thread diameter, the precipitating liquid being ether tating bath ning solution percent 52 1 53? and the threads obtained being collected on bobbins or in a centrifugal.

Degrees n 1 11 4.9 1% 25.; 3 so 1 1 a 21. 84 Temperature COIPCCDW of Elonga- .stlengthl -20 1 11 3 1 23 1 25 of reci tion of single tiouin single thread 40 tatgqg g spinning thread: percent in grams per solution demcrs denier Example 5 De ms A cellulose acetobutyrate containing 8% bu- 1:9 22 34 tyric acid and dissolved in a mixture of 95 parts gi methylene chloride and 5 parts alcohol was spun 9 5 1 26 1 and precipitated in ether.

0 139 18 Temperature Conccntrag Elongation f g 0 119 2 15 of precipition of spin- .5: in $11156 1:9 T6 tating bath ning solution i percent g 55 it t it it t? -20 11-11 2I4 15 1.80 -30 1:13 2. 7 15 2.7 Degrees -30 1:13 2.0 14.5 2.05 +18 1:11 2.88 25 5 1.13 -10 1:13 3. 5 12. 5 2. 23 -10 111 2.87 17 1. 54 1:13 1.8 10 2. 34 1:11 3.09 15 1.79

Similarly as the cellulose esters mentioned above also other simple cellulose esters, such as the formates, propionates or butyrates or mixed cellulose esters, such as the acetoformates, acetopropionates or acetobutyrates, as well as the products obtained by subjecting the primary esters to a more or less far reaching hydrolytic decomposition may be subjected to the new process, the most suitable solvents being used in each individual case.

We have found that when proceeding in accordance with this invention, i. e. introducing the cellulose ester solution into a coagulating liquid cooled down to at least +2 C., we may also use, as solvents for the esters, solvents or solvent mixtures which are known to be unsatisfactorywhen coagulation is effected at a higher temperature. Thus for instance solutions of mixed esters in a mixture of 95 parts ethylene chloride and 5 parts ethyl alcohol or in a mixture of 23 parts acetone and parts dioxan can be coagulated and yield strong threads in a coagulation liquid cooled down to at least +2 C. and preferably to 20 0.

Instead of ether and toluene also other precipitants, such as benzine, petroleum, cyclohexan and others may serve for precipitating the esters.

Instead of spinning solutions of isolated cellulose esters, it is also possible in some cases to directly spin the solutions obtained in the production of the cellulose esters, as is known in the spinning processes carried through at higher temperatures.

It will be interesting to know that when proceeding in accordance with the present invention, the precipitating liquors can be used much longer without being regenerated, than can be done in a process operating at higher temperature, because the precipitating efiect is preserved at the low temperatures even if the liquor is highly diluted by the solvents.

Operation at low temperature also counteracts the losses encountered when using readily volatile liquids for precipitating the esters.

Various changes may be made in the details disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

We claim The method of coagulating solutions of carboxylic acid esters of cellulose comprising introducing the solutions into a neutral organic coagulating liquid having a melting point below +2 C. and cooled below +2 C.

RICHARD MiiLLER. ALFRED LI'iBKE. 

